Efforts will be made to further extend the applicability of electromagnetic flow measuring methods by efforts to miniaturize extractable flow probes. Probes currently in use will be implanted on the external iliac vessels of the dog at periods of one to several weeks with chronic flow recording. Additional studies into renal hemodynamics will be carried out using the isolated renal blood flow preparation previously described from this laboratory. This permits the measurement of total renal blood flow as it is carried through a single subcutaneous conduit. It also permits the injection of test substances directly into the renal circulation by percutaneous puncture of the subcutaneous conduit. New studies are planned for the investigation of the relationship of intestinal blood flow to intestinal secretion. Artificially induced high flow and low flow states will be produced in experimental animals to investigate their influence on gastro-intestinal secretion.